The invention relates to a scanning probe sensor. The invention further concerns a related scanning probe microscope, a related method and a related computer program product.
Various scanning probe microscopy techniques exist to image surface and electrical properties of samples down to nanoscopic and even atomic scale. All these techniques rely on scanning probes, typically comprising a sharp tip, in close proximity or even in contact with a sample surface to monitor interactions between the probe and the sample, e.g. force or tunnel current. The signal measured is fundamentally related to the shape (sharpness, opening angle) of the scanning probe defining the tip-sample contact. A sharp tip is typically required to achieve high spatial resolution down to atomic and even intermolecular resolution limits. The fabrication of a sharp scanning probe tip is challenging but tip apex radii below 10 nm can typically be achieved by present day electron beam lithography.
The exact shape of the tip apex, however, is typically not fully controlled in the manufacturing process. Scanning electron microscopy (SEM) is frequently applied to better describe the tip before measurement. Other techniques to characterize the tip shape are based on reverse imaging techniques and mathematical reconstruction of the apex shape by imaging surfaces of well defined, known topographies. If the surface topography is unknown, blind-reconstruction is applied to quantify the tip apex shape.
Despite these possibilities to measure the tip shape, remaining uncertainties and the continuous changing of tip shape during the measurement remain a challenge in the use of scanning probe microscopy methods for quantitative analysis. Controlling and maintaining the tip shape is critical for scanning probe measurement signals which are acquired by a convolution of the sample properties to be characterized and the properties of the scanning probe tip itself.
Dynamic scanning modes, also denoted as non-contact scanning modes, have been developed to achieve high spatial resolution in order of a few nanometers. Using these modes of operation, the interaction forces between the probe tip and the sample can be controlled very precisely. This has enabled imaging of liquid droplet surfaces.